"For many years," Donald Trump tweeted Sunday afternoon, "our country has been divided, angry and untrusting. Many say it will never change, the hatred is too deep. IT WILL CHANGE!!!!"

As persuasive as the ALL CAPS are, I have my doubts.

Put aside Trump's specific shortcomings for the moment. The presidency has become ill-suited to the task of unifying the country, because the presidency has become the biggest prize and totem in the culture war. Like the religious wars between Catholics and Protestants in England, if one side controls the throne, it is seen as an insult and threat to the other. And whoever holds the throne is seen as a kind of personal Protector of the Realm.

The political parties have been utterly complicit in the process. Exploiting social media and other technologies, Republicans and Democrats shape their messages around the assumption that they -- and they alone -- have legitimate ownership of America's authentic best self. That's why whichever party is out of power promises to "take back America" -- as if the other side were foreign invaders.

Barack Obama was elected in 2008 in no small part to fulfill the promise of his 2004 Democratic Convention keynote address: to banish the slicing and dicing of America into Red States and Blue States.

The colors of the electoral map may have been smudged and scrambled over the last eight years, but the underlying polarization Obama inherited from George W. Bush only intensified on his watch. Trump will be the third president in a row to promise to unite the country, and he will almost certainly be the third in a row to fail.

The ugly squabble between the president-elect and Rep. John Lewis (D-Ga.) over the weekend offers a glimpse into how bad things will get.

Lewis earned his icon status on the Edmund Pettus Bridge on Bloody Sunday in Selma, Ala. But over the years, he's traded some of his moral capital for partisan chips, insinuating that only the Democratic Party has ownership of the civil rights era and its victories, despite the fact that a higher share of Republicans voted for the Civil Rights Act than Democrats. Indeed, the goons who cracked Lewis' skull on the Edmund Pettus Bridge were acting at the behest of a Democratic governor and Democratic local officials. Even the bridge was named after a Democrat.

In 2008, Lewis saw nothing wrong with comparing Sen. John McCain (R-Ariz.) to the segregationist Alabama Gov. George Wallace, adding: "Sen. McCain and Gov. [Sarah] Palin are sowing the seeds of hatred and division." He did it again in 2012, insinuating that voting for Mitt Romney might lead America to "go back" to the days of fire hoses, police dogs and church bombings.

This was not idealism, but poisonous cynicism, and it helped contribute to the feelings of resentment that were so essential to Trump's victory. Now, Lewis is going further still, refusing to attend Trump's inauguration and arguing that Trump cannot be a legitimate president because of Russian meddling in the election. Lewis may have reason to believe that Trump did not win fair and square, but questioning Trump's legitimacy is exactly what the Russians probably wanted from the beginning: to undermine Western and American faith and confidence in democracy. (It's a sign of Lewis' partisanship that he also boycotted George W. Bush's first inauguration because he didn't think Bush was legitimate either.)

Of course, Trump made things worse. He attacked Lewis, saying the congressman "should finally focus on the burning and crime infested inner-cities of the U.S." instead of "falsely complaining about the election results." Predictably, Democrats rallied behind Lewis, who's basically the party's living saint, and they're already fundraising off the spectacle.

The Democrats will stop baiting Trump when he shows he can refuse the bait. Which means they won't stop.

There's an almost literary quality to Trump's insecurities; he craves respect more than almost anything else, and yet respect remains agonizingly elusive -- in part because he takes everything too personally.

The presidency, normally a job for people with thick skins and a nose for insincere flattery, promises to only heighten Trump's sense of entitlement to respect and exacerbate his inevitable resentment when he doesn't receive it. So we'll continue on divided, angry and untrusting.